1. Field of the Invention
The present invention relates to a sanitary safety device, especially for a sanitary fitting, for preventing the backflow of water into a feed conduit.
2. Discussion of the Background
Safety devices of this type are known from U.S. Pat. Nos. 2,270,737 and 2,382,427. They are provided in order to be installed in toilet flushing devices between the flushing cock and the flushing pipe leading to the toilet. They are installed in a vertical direction and at a considerable vertical distance above the dirty water which is possibly present in the toilet bowl and which could be sucked back. In flushing devices of this type, therefore, in the event of low negative pressures prevailing on the feed side, there is no risk that dirty water will pass into the feed conduit. The known safety devices consequently have to function reliably only in the event of a considerable negative pressure prevailing on the feed side.
The safety devices known from the publications mentioned have a sleeve-shaped valve body made of elastomeric material, which is arranged inside a tubular housing and which is fastened by means of its fastening end located on the inlet side to an inner flange of the housing. The valve body engages around a bell-shaped thin-walled valve-seat element, of which the bottom region facing the inlet of the housing is fastened to a web-like supporting member which is itself supported fixedly relative to the housing. The valve-seat element cooperates, by means of its flank end region located downstream, with a free end portion of the valve body, said end portion being widened in a bell-like manner and being remote from the fastening end, the rim of the valve-seat element being set back relative to the free end of the valve body. The housing has a second inner flange which is intended for cooperating with the outside of the end portion of the valve body when water flows through the latter, in order to separate the ventilation orifices, present above the second inner flange, as seen in the direction of flow of the water, and connected to the ambient air, from the outlet orifice of the housing. When no water flows through the safety device and no negative pressure prevails on the inlet side, the valve-seat element is on the valve body, and between the latter and the second inner flange there is a ring-like ventilation gap which connects the ventilation orifices to the outlet orifice in terms of flow. Under these conditions, the outlet orifice is therefore ventilated. When water flows, under the pressure of the water, on the one hand the valve body expands and is laid with its end portion against the second inner flange, and on the other hand the valve-seat element is bent inward in the direction of flow and in the radial direction, thus necessarily leading to folding or kinking in the valve-seat element. Under the negative pressure prevailing on the feed side, the valve body and the valve-seat element are pressed against one another as a result of the squeezing suction pressure, the trickling gap between the valve body and the inner flange of the housing remaining open, in order to ventilate the outlet orifice.
These known safety devices are designed for the high throughflow quantities per unit of time necessary for the flushing of toilets, but would seem not to have a reliable operating behavior for only small water quantities flowing through and not to be suitable for purposes other than use in toilet flushing devices. Since the expansion of the valve body would seem to require more force than the inward folding of the thinwalled valve-seat element, with small throughflow quantities there is no guarantee that the valve body will be laid with its end portion against the second inner flange of the housing. Under these operating conditions, therefore, should water be capable of flowing back on the outlet side, there is the risk that this water can escape through the ventilation orifices. Furthermore, the valve body should not bear under a prestressed condition on the valve-seat element, because it would then no longer be guaranteed that, after the interruption of the water flow, the valve-seat element folded inward by flowing water will be laid flush against the valve body again, because the folded valve-seat element cannot exert the force to expand the valve body correspondingly. Moreover, known safety devices are, for example, unsuitable to be used in hose-type shower fittings, since there, when the water flow is interrupted, water trapped in the shower hose can escape through the ventilation orifices when the shower is lifted, and this is not permissible, particularly in kitchen fittings of this type.
An object of the present invention is, therefore, to provide a safety device of the relevant generic type, which can be used universally and which functions in a reliably safe manner under all operating conditions. This object is achieved by means of the safety device of the present invention.
Since the valve body, in a state of rest, that is to say with equal pressure on the inlet side and on the outlet side, bears on the ventilation-valve seat and thus separates the ventilation orifices from the outlet orifice, the outflow of water through the ventilation orifice is prevented even when the water flow coming from the feed conduit is interrupted. Since the valve-seat element is of a fold-resistant and kink-resistant design and the valve body bears on the latter under prestressing in a sleeve-like manner, it is always necessary, with water flow, however small, coming from the feed conduit, for the valve-seat element to expand in order to release the water flow between it and the valve-seat element. Thus, in the event of water flow, the pressure is always higher upstream of the valve-seat element in the flow channel enclosed by the valve body than underneath the valve-seat element in the direction of flow, thereby always ensuring, even under these conditions, that the valve body bears on the ventilation-valve seat and prevents the outflow of water through the ventilation orifice. However, a continuous bead guarantees that, even under a low negative pressure prevailing on the feed side, the valve body lifts off immediately from the ventilation-valve seat and allows for ventilation of the outlet orifice. This bead makes it possible to contract the valve body in the radial direction, without the latter at the same time having to expand in the axial direction. The length compensation takes place with very little effort by means of the bead.
In an especially preferred embodiment of the present invention, the risk that, with water flowing in from the outlet side, the valve body can peel off from the valveseat element is reduced.
A further preferred embodiment affords reliably safe functioning, even if a foreign body were to penetrate between the valve-seat element and the valve body. The prestress of the valve body and, in particular, the design of the valve body and of the valve-seat element in the manner of a sealing lip ensure that the foreign body is tightly enclosed.
The likewise additional preferred embodiments of the safety device according to the invention afford a particularly simple construction and allow for extremely simple assembly.
A further advantageous embodiment makes it possible to support the valve body carefully when water is supplied at high pressure. The arrangement of a supporting and holding sleeve ensures that the radial widening of the valve body is limited and the risk of damage to the valve body is eliminated. Moreover, an especially simple assembly can likewise be brought about.
Especially preferred sanitary fittings having the safety device according to the invention are also part of the present invention.